Flexible rotochute



Dec. 31, 1963 H. SUTER FLEXIBLE ROTOCHUTE Filed Sept. 26, 1961 F fg. I

INVENTOR. HENRY SUTER ATTORP'E Navy Filed Sept. 26, 1961, Ser. No. 14%,956 5 Claims. (Cl. 102- 4) (Granted under Title 35, Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

The present invention relates to rotary-wing parachutes, and more particularly to a rotary-wing parachute for effecting smooth deceleration of a projectile from a high initial velocity to a low terminal velocity.

Rotary-wing parachutes, hereinafter referred to as rotochutes, are usually constructed of an array of rigid metal vanes radially extending from a bearing journaled on the posterior end of a projecitle. The vanes are pitched so that any axial Wind will cause them to revolve about the projectiles longitudinal axis. For high density storage, the vanes are usually hinged at the bearing with their free ends adjacent to the sides of the projectile and forward of the bearing. When the projectile is launched, the wind causes the vanes to swing to a radially extended and retarding position. The vanes are restrained against swinging little more than 90 degrees from the longitudinal axis. At high launching speeds the vanes swing outward suddenly and impart a very high initial deceleration force to the projectile. This force often creates intolerable stresses on both the rotochute mechanisms and on any delicate parts contained in the projectile.

In certain types of projectiles, such as air-launched sonobuoys which are dispatched into the sea, the rotochute must also be jettisoned before other functions become operative. Since the rotochute is rotating at a very high velocity at the time of entry into the Water, damage often occurs after the detachment caused by the spinning vanes striking parts of the sonobuoy.

Accordingly, it is an object of the present invention to provide an improved rotochute for smoothly decelerating a projectile launched at a high velocity to a low terminal velocity, which progressively retards the projectile without introducing undesirable shock and intolerable stresses, in which the retarding effect varies inversely with the velocity of the projectile, and in which the vane area exposed to the air stream varies directly with the Wind force on the vanes.

Another object is to provide an improved rotochute suitable for use with an air-launched sonobuoy, in which the deceleration force imparted on the sonobuoy by the rotochute upon entry into water is substantially eliminated, and in which the rotochute functions as a stabilizer for the sonobuoy against wave action after water entry.

Still another object of the invention is to provide a rotochute which is greatly simplified in construction, relatively low in cost of materials and manufacturing, and which is reliable and efficient under severe operating conditions.

Various other objects and advantages will appear from the following description of one embodiment of the invention, and the most novel features will be particularly pointed out hereinafter in connection with the appended claims.

In the drawings:

FIG. 1 represents a longitudinal view of a projectile with a rotochute of the present invention in the retracted and nonretarding position;

FIG. 2 represents the rotochute of FIG. 1 in a posiat E "ice tion immediately after launching superimposed, in a phantom view, by the rotochute in the fully extended position;

FIG. 3 represents a crosssectional view of one vane of the rotochute of FIG. 2 taken along the line 3-3; and

FIG. 4 represents a side view of the vane shown in FIG. 3 taken along the line 4-4.

in the illustrated embodiment of the invention, a projectile it) is formed at the rearward end with a plurality of recesses 11. An array of elongated flexible vanes 12, positively rooted in the recesses 11 by any convenient means, are equally spaced around the projectile with their transverse axes angularly displaced from a plane normal to the longitudinal axis of the projectile an amount equal to the desired root pitch of the vanes 12. This amount is shown by the angle 9 in FIG. 3. One material employed for the flexible vanes 12 is rubber; however, other materials alone or in combination are contemplated which give the desired deflections for the expected wind and centrifugal forces. In applications where the projectile it lands in the water, the vane material should also be of relatively low specific gravity so as not to adversely affect flotation of the projectile Ill at water entry since the vanes 12 remain attached. It is also contemplated that the rooted ends of the vanes 12 may be thickened or reinforced to provide selective stiffening and twisting throughout their length so that they will deflect the correct amount throughout the trajectory of the projectile Hi.

The operation of the rotochute should now be apparent. When the projectile it) enters the air stream, the vanes 12 immediately bend backwards. Due to the root pitch of the vanes 12, a pin wheel effect causes r0- tation of the complete assembly of the vanes 12 and the projectile 1t).

FIGS. 3 and 4 illustrate the manner in which the rooted end of the vanes 12 react against the wind force. Immediately after launching, the vanes 12 bend rearwardly about a radius r to produce a projected surface at the vane roots angularly displaced from the plane normal to the air stream by the angle 6. A low drag, high torque condition thus exists and the projectile l0 and vanes 12 commence to rotate. As the rotation and centrifugal force progressively increase, the vanes 12 will gradually move from the position shown in solid lines in FIG. 2 to a position shown in phantom where the vanes 12 are substantially normal to the longitudinal axis of the body or projectile 1d. The vanes 12 thus provide a progressively increasing lift action resulting in a speed transition of a controlled character.

It will be noted that the area exposed to the air stream varies directly with the air force on the vanes 12. Initially, the vanes 12 are bent backwards exposing only a small area to the air. As the projectile 10 begins to rotate, the centrifugal forces exerted on the vanes 12 cause them to extend radially from the axis of rotation thus exposing a larger area of the vanes 12, hence a gradual deceleration of the projectile Till.

In applications where the projectile it is launched from an aircraft into water, it will be observed that the vanes 12 will bend backwards again offering relatively little drag as the rotochute enters the water. A stabilizing function is also provided by the vanes 12 in applications where the projectile 10, such as a sonobuoy, floats after entry into Water. As the projectile 10 tends to sink below the crest of a wave due to its inertia, the vanes 12 bend upward and the water motion imparts an upward force on the projected area. Then when the wave passes, the water motion will not impart an appreciable downward force because the vanes 12 return to their normal, unstressed position against the sides of the projectile.

It is thus seen that the rotochute of the present invention provides an inexpensive, simple means for gradually retarding the speed of an air-launched projectile during both its air trajectory and its entry into water resulting in less chance of damaging shock to any parts contained in the projectile.

It will be understood that various changes in the details, materials, steps and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the appended claims.

What is claimed is:

1. A projectile capable of being launched at a relatively high initial velocity and retarded to a relatively low terminal velocity comprising: an elongated cylindrical casing streamlined for aerodynamic stability, the longitudinal axis of said casing being the axis of rotation of said projectile, a plurality of normally flat parallel blades contiguously wrapped around said casing in helical relation to said axis of rotation, said blades being universally flexible throughout their lengths, means for rigidly securing the rearwardly disposed ends of said blades adjacent to the posterior end of said casing on a surface inclined transversely to the axis of rotation of said projectile, the angle of inclination determining the root pitch of said blades; whereby said blades develop torque about said axis of rotation when deflected rearwardly about their secured ends by airflow, and gradually move radially outward due to centrifugal forces produced by the rotation of said blades to develop lift.

2. A projectile capable of being launched at a relatively high initial velocity and retarded to a relatively low terminal velocity comprising: a casing streamlined for aerodynamic stability, a plurality of normally flat lades universally flexible throughout their length wrapped around said casing on a helix angle corresponding to a desired root pitch of said blades, means for permanently securing the rearwardly disposed ends of said blades near the posterior of said casing along transverse surfaces of said blades; whereby said blades develop rotational torque about the longitudinal axis of said casing when deflected rearwardly about their secured ends by airflow, and gradually move radially outward due to centrifugal forces produced by the rotation of said blades to develop lift.

3. A projectile capable of being launched at a relatively high initial velocity and retarded to a relatively low terminal velocity comprising: a casing streamlined for aerodynamic stability, a plurality of fiat elongated elements helically wrapped around said casing in parallel relation to each other, said elements being universally flexible throughout their lengths, means for rigidly securing the rearwardly disposed ends of said elements adjacent to the posterior end of said casing; whereby said elements rotate When deflected rearwardly about their secured ends by airflow, and gradually extend radially to develop lift.

4. A rotochute for smoothly decelerating a projectile launched at a relatively high initial velocity to a relatively low terminal velocity comprising: an array of normally flat vanes adapted to be permanently secured at their innermost ends at equally spaced intervals around the circumference of the projectile near the posterior end thereof, each of said vanes being universally flexible throughout its length and its end-to-end axis being inclined transversely. to the longitudinal axis of the projectile an amount corresponding to a desired root pitch therefor; whereby said vanes develop rotational torque about the longitudinal axis of the projectile when deflected rearwardly about their secured ends by airflow, and gradually extend radially due to centrifugal forces produced by the rotation of said vanes to develop lift.

5. A rotochute for smoothly decelerating a projectile launched at a relatively high initial velocity to a relatively low terminal velocity comprising: an array of normally flat vanes universally movable between an operative and inoperative position and being flexible throughout their lengths, said vanes adapted to be wrapped around the surface of the projectile on a helix angle corresponding to a desired root pitch for said vanes, means for permanently securing the innermost ends around the circumference of the projectile near the posterior end thereof, said vanes having their end-to-end axes inclined transversely to the longitudinal axis of the projectile when said vanes are in said inoperative position.

References Cited in the file of this patent UNITED STATES PATENTS 35,503 Browne June 10, 1862 1,318,926 Settle Oct. 14, 1919 2,044,819 Taylor June 23, 1936 2,324,146 Frazer July, 13, 1943 2,918,235 Aberg et al. Dec. 22, 1959 2,969,211 Von Saurma Jan. 24, 1961 3,016,217 Polleys et al. Jan. 9, 1962 

1. A PROJECTILE CAPABLE OF BEING LAUNCHED AT A RELATIVELY HIGH INITIAL VELOCITY AND RETARDED TO A RELATIVELY LOW TERMINAL VELOCITY COMPRISING: AN ELONGATED CYLINDRICAL CASING STREAMLINED FOR AERODYNAMIC STABILITY, THE LONGITUDINAL AXIS OF SAID CASING BEING THE AXIS OF ROTATION OF SAID PROJECTILE, A PLURALITY OF NORMALLY FLAT PARALLEL BLADES CONTIGUOUSLY WRAPPED AROUND SAID CASING IN HELICAL RELATION TO SAID AXIS OF ROTATION, SAID BLADES BEING UNIVERSALLY FLEXIBLE THROUGHOUT THEIR LENGTHS, MEANS FOR RIGIDLY SECURING THE REARWARDLY DISPOSED ENDS OF SAID BLADES ADJACENT TO THE POSTERIOR END OF SAID CASING ON A SURFACE INCLINED TRANSVERSELY TO THE AXIS OF ROTATION OF SAID PORJECTILE, THE ANGLE OF INCLINATION DETERMINING THE ROOT PITCH OF SAID BLADES; WHEREBY SAID BLADES DEVELOP TORQUE ABOUT SAID AXIS OF ROTATION WHEN DEFLECTED REARWARDLY ABOUT THEIR SECURED ENDS BY AIRFLOW, AND GRADUALLY MOVE RADIALLY OUTWARD DUE TO CENTRIFUGAL FORCES PRODUCED BY THE ROTATION OF SAID BLADES TO DEVELOP LIFT. 